Dyeing of leather



United States Patent IO 2,893,811 DYEING F LEATHER Joseph S. Kirk, EastGreenbush, N.Y., assignor to General Aniline & Film Corporation, NewYork, N.Y., a corporation of Delaware No Drawing. Application December30, 1955 Serial No. 556,439

4 Claims. (Cl. 8 -12 The instant invention relates to improvements inthe dyeing of leather, and more particularly to a process for processfor dyeing leathers of the above-mentioned type with direct dyestuffs.Another object is the provision of a novel composition for the dyeing ofsuch leathers with direct dyestuffs. pear as the description proceeds.

Other objects and advantages will ap- The attainment of the aboveobjects is made possible by the instant process which comprisesdyeingleather tanned with a member of the group consisting of vegetabletanning extracts and aqueous solutions of formaldehyde and a polyhydricphenol of the group consisting'of resorcinol and pyrogallol with adirect dyestutf from an aqueous dyebath at a pHv of about 5 /21to7containing about 0.1 to 5%, basedon the weight of the leather, of awater-soluble non-ionic surface active condensation product having theformula wherein R is a straight chain aliphatic hydrocarbon radical offrom 16 to 18 carbon atoms and n has a value of about 12 to 18. It hasbeen found that the use of the above defined dyebaths results inoutstanding dyeings which are in general fuller, clearer, brighter andmore uniform and/or level than dyeings produced without the assistanceof the above defined non-ionic surface active agents. Moreover, theresulting dyed leather has an improved hand and feel, and is less,brittle, harsh andraspy.

The process of this invention produces improved dyeing results whenapplied to leather which has been treated with vegetable tanningextracts. The treatment with vegetable tanning extracts and the effectsthereof are well known in the art and no claim is made thereto per se.Vegetable tanning extracts contain tannins as their active principal,cutch, quebracho, gambier, myrobalan, chestnut and wattle extractshaving been found to yield excellent results in the process of thisinvention. Vegetable extracts are usually applied in proportions ofabout 5 to 15% by weight of the leather for retannage of chrome leatherand about 30 to 100% by weight of the skin for complete tannage.

The process of this invention is also applicable for producing improveddyeing results when applied to leather which has been treated or tannedwith aqueous solutions of formaldehyde and resorcinol or pyrogallol.Such treatments are also well known in the art, as represented forexample by the tanning process disclosed in US.

; desired, and the like.

0.1 to 5% of dyestutf by weight of the leather are usually Patent No.2,552,129. Such treatment generally involves application to the hides,skins, and pelts of an aqueous solution containing the formaldehyde andpolyhydric phenol in respective molar proportions of at least 2:1 at apH of about 0.3 to 3.0, as more fully described in said patent. It willbeunderstood that instead of formaldehyde, there may be employedpolymers of formaldehyde, acetaldehyde, crotonaldehyde, benzaldehyde,furfural and the like. Similarly, nuclear derivatives of resorcinol andpyrogallol may be employed, as for example hexylresorcinol, tertiaryoctylresorcinol, benzylresorcinol, phenylresorcinol, methoxyresorcinol,and the like. Mixtures of the aforementioned aldehydes and polyhydricphenols may also be employed, and the treatment may be applied inconjunction with other well known tanning treatments such as withvegetable tanning extracts, chromium sulfate, aluminum sulfate,zirconium sulfate, and the like.

. The direct dyestuifs employed in the instant invention are also wellknown in the art, being generally of the anionic type resulting from thepresence therein of carboxylic or sulfonic groups. It will be understoodthat the term direct dyestuff also includes those direct dyestuffs whichare ,chromable by reason of containing metallizable groups capable offorming complexes with chromium. Highly satisfactory results areattained when'such metallizable groups consist of anortho-hydroxycarboxy configuration relative to an azo bridge ascontained, for example, in azo dyestuffs produced with aparaaminosalicylic acid diazo component. Examples of direct, includingdirect chromable dyestuffs operative in the process of the instantinvention are disclosed in the examples below. Other suitable dyestuffs"include -for example Fastusol Brown RTA (Pr. 365) and Direct Green YYD(Cl. 594). Since the process proceeds by exhaustion,

the amount of dyestuff'in the dyebath will be dependent upon the amountof leather treated, the depth of shade Generally, proportions of aboutemployed for the production of light shades, 5 to 10% for medium shadesand 10 to 20% for heavier shades.

The dyebaths of the instant invention are employed inwell known mannerat temperatures ranging from about room temperature to 150 F.,temperatures of about 120 to 140 F. being preferred. Best results areusually obtained by adding an acid, preferably organic, such as formicacid, towards the end of the dyeing process in order to complete theexhaustion of the dye on the leather. As stated above, the instantdyebaths are applied at an initial pH ranging from about 5% to 7,although this pH may drop somewhat during the dyeing process due to acidsubstances in the leather being dyed.

From the above, it will be understood that the instant inventionresidessolely in the use, in the known processes for dyeing leather with directdyestufis, of about 0.1 to 5%, based on the weight of'said leather, of awater- .soluble non-ionic surface active agent of the type definedabove. Optimum results are usually attained with about 1 to 3% of saidsurface'active agent by weight of the leather. Dyebaths employed incarrying :out the process of this invention usually contain about0.2 to3 parts of ,,the said non-ionic surface active agent- -for each p-art ofdirect dyestuif, by weight 'Said agents,=and their methods of productionare well known in the art and no claim is made thereto per se. Referenceis made to US. Patent No. 1,970,578 for a disclosure of such surfaceactive agents and their methods of production. In general, they may beproduced by condensation of a higher fatty amine such as hexadecylamine,heptadecylamine, octadecylamine and their unsaturated analogs such asoctadecenylamine and the like, or mixtures thereof, with 12 to 18 molesof ethylene oxide or equivalent. The above amine employed forcondensation with ethylene oxide may be Patented July 7, 1959 3 derivedin known manner from animal, vegetable, or mineral oils, fats and waxes,or in any other suitable manner.

The following examples, in which parts are by weight unless otherwiseindicated, are illustrative of the instant A control set of dyeings wasalso carried out without the use of Agent A. In all cases, improvedresults with respect to levelness, clearness, fullness, brightness,and/or hand were obtained with the use of Agent A as compared withresults obtained without the use of Agent A.

invention and are not to be regarded as limitative. In This inventionhas been disclosed with respect to certhe examples, Agent A is thecondensation product of tain preferred embodiments, and variousmodifications 15 moles of ethylene oxide with 1 mole of a mixture of andvariations thereof will become obvious to persons amines consisting ofabout 30% hexadecylamine, 25 skilled in the art. It is to be understoodthat such modioctadecylamine, and 45% octadecenylamine by weight.fications and variations are to be included within the The resorcinolformaldehyde-alum tanned calfskin emspirit and purview of thisapplication and the scope of ployed in the examples is produced bytreatment of calfthe appended claims. skin in a manner similar to thatdisclosed in Example I claim: of US. Patent 2,552,129 employing aluminstead of zir- 1. In a process for dyeing leather which has been coniumsulfate. It will of course be understood that 5 tanned with a member ofthe group consisting of vegeleather produced in a similar manner butwithout the use table tanning agents and aqueous solutions of formaldeofalum also yields improved results when dyed by the hyde and a polyhydricphenol of the group consisting of process of they instant invention.resorcinol and pyrogallol, the improvement comprising In the followingexamples, a 5 g. sample of resorcinoldyeing such leather with a directdyestuif from an aqueous formaldehyde-alum tanned calfskin was wet backin 100 dyebath at a pH of about 5% to 7 containing about 0.1 cc. watercontaining 2%. Emulphor ON wetting agent to 5%, based on the weight ofthe leather, of a water- (General Aniline & Film Corporation;polyoxyethylene soluble non-ionic surface active agent having theforether of a higher fatty alcohol). The leather was rinsed mulaR-NH--(CH CH O),,H, wherein R is a straight and entered in a dyebathcontaining about cc. water, chain aliphatic hydrocarbon radical of from16 to 18 car- .05 g. dyestuff and .1 g. of Agent A. The bath was main-25 bon atoms and n has a value of about 12 to 18. tained at 120 to 130F. for minutes, and then .025 g. 2. A process as defined in claim 1wherein said nonformic acid was added. After maintaining the bath forionic surface active agent is the condensation product of another 30minutes the leather was rinsed and dried. The about 15 moles of ethyleneoxide with 1 mole of a mixresults are tabulated below. ture of aminesconsisting essentially of about 30% hexa- TABLE Ex. Dye Identity ResultsWithout Agent A. Results with Agent A Fastusol Orange Level, fair colorLevel, much stronger.

L3RA

Fastusol Brown LBRSA Fastusol Yellow LRTP Fastusol Green BA Level, fairgood color N ot level, fair color- Level, very good color.-- Level,bright, fair color Level, bright, good color N 01; level, fair color--was spotty, fair colo o Dull, grayish blue, very poor- Very littlecolor, very poor Spotty, little color, very poor Spotgy, very littlecolor, very poor M h b Stronger, fuller, brighter.

Level, very full, bright.

Very much fuller and redder.

Duller, much fuller.

Do. Level, very full. verybtull rich red.

Stronger.

Full deep blue.

Level, full deep blue.

0 ette u r. Full bright turquoise.

Fastusol Turquoise Blue LGAM- The dyestufls employed in the abovetableand their identity are listed in the 1954 Yearbook of the AmericanAssociation of Textile Chemists and Colorists (AATCC).

In all cases, the dyed. leather had an improved hand and feel, and- Wasless brittle, harsh and raspy when employing Agent A as compared withresults obtained Without the use of Agent A.

Example 15 The procedure of the above examples was repeated with thefollowing dyestufis, but employing a 5 g. sample of sheepskin mordantedwith 10% of quebracho extract based on the set blue chromed weightinstead of the resorcinol formaldehyde-alum tanned calfskin, .25 g. ofdyestufi instead of .05 g. of dyestufi, and .09 g. of Agent A instead of.1 g. of Agent A.

Fastusol Orange LBRA Fastusol Brown LBRSA Fastusol Blue LR. Fastusol RedAPA Fastusol Green BA decylamine, 25% octadecylamine and 45%octadecenylamine, by weight.

3. A process as defined in claim 2 wherein the leather has been tannedwith a vegetable tanning extract.

4. A process as defined in claim 2 wherein the leather has been tannedwith an aqueous solution of formaldehyde and resorcinol.

References Cited in the file of this patent UNITED STATES PATENTS

1. IN A PROCESS FOR DYEING LEATHER WHICH HAS BEEN TANNED WITH A MEMBEROF THE GROUP CONSISTING OF VEGTABLE TANNING AGENTS AND AQUEOUS SOLUTIONSOF FORMALDEHYDE AND A POLYHYDRIC PHENOL OF THE GROUP CONSISTING OFRESORCINOL AND PYROGALLOL, THE IMPROVEMENT COMPRISING DYEING SUCHLEATHER WITH A DIRECT DYESTUFF FROM AN AQUEOUS DYEBATH AT A PH OF ABOUT51/2 ATO 7 CONTAINING ABOUT 0.1 TO 5%, BASED ON THE WEIGHT OF THELEATHER, OF A WATERSOLUBLE NON-IONIC DURFACE ACTIVE AGENT HAVING THEFORMULA R-NH-(CH2CH2O)2H, WHEREIN R IS A STRAIGHT CHAIN ALIPHATICHYDROCARBON RADICALS OF FROM 16 TO 18 CARBON ATOMS AND N HAS A VALUE OFABOUT 12 TO 18.